Planarization Efficiency of Electrochemical Mechanical Deposition and Its Dependence on Process Parameters

Abstract

Electrochemical mechanical deposition (ECMD) is a technique that has the ability to deposit planar metal films on nonplanar substrate surfaces with cavities. The method involves electrochemical deposition and simultaneous sweeping of the substrate surface with a planarization pad. Mechanical action of the pad increases suppression at the swept surface and therefore, mechanically induced superfilling of the cavities takes place. In this study we show that the planarization efficiency of the ECMD process for copper deposition is a strong function of the plating chemistry. Electrolytes containing no organic additives or only accelerators do not yield any planarization. Plating baths with only suppressors show low planarization capability, whereas those containing both suppressors and accelerators yield the highest planarization efficiency. Soaking the wafer surface in an accelerator-containing solution before the ECMD process step increases the planarization efficiency significantly. The presence of levelers in the plating electrolyte is detrimental to planarization efficiency of ECMD. High-acid copper plating solutions display higher planarization capability than low-acid electrolytes.